DENVER – Parents held tight to their sobbing children on Tuesday after two students interrupted classes with gunfire, killing one and injuring eight others at a suburban Denver STEM school.

All of the shooting victims are students ages 15 and older. The male student who died was 18 years old, the sheriff tweeted at 6:45 p.m. MDT.

The shooting suspects are in custody, Douglas County Sheriff Tony Spurlock said. One is an male juvenile and the other was identified by police as Devon Erickson, 18.

"We will not be releasing any photos at this time as it could jeopardize this critical on-going invest," the sheriff said on Twitter. "We still have interviews to conduct and we want to make sure we have the most accurate information."

Robert Helfer, 13, was in math class when he heard a disturbance.

“Everyone thought it was a theater play at first. Then when we just started hearing banging and gunshots and cursing,” the seventh-grader said, his eyes red, his shaking hands twisting a plastic water bottle. “There was a body by the door when the police officer came to get us.”

Spurlock said the suspects opened fire in two separate classrooms at STEM School Highlands Ranch, a public charter school with more than 1,850 students in kindergarten through 12th grade.

Bharani Rayana, 39, and Madhuri Adari, 32, hold tight to their second-grade son Daksha Rayana 8, following reunification at the Highlands Ranch Recreation Center after a school shooting.(Photo: Trevor Hughes, USA TODAY)

Police responded to the shooting before 2 p.m., arriving quickly because there is a law enforcement substation nearby. Deputies engaged the suspects and took them into custody without injuring them, Spurlock said.

Two of the injured are in serious condition, two are in stable condition and one is in good condition, area hospitals said. Three of the injured have been discharged, Littleton Adventist Hospital spokeswoman Wendy Forbes told USA TODAY.

"This is a terrible event," Spurlock said. "This is something that nobody wants to happen in their community. We're going to investigate that and we will get to the bottom of it to figure out how and what has occurred."

The sheriff’s office directed parents to a recreational center to reunite with their children.

Andrea Pedatto, 46, was installing a ceiling fan at her nearby home when she got the news her son’s school was under attack. Her husband burst into tears in frustration while she swung into action, grabbed their Yorkie, Stella, and headed to the center.

“I wasn’t panicking because they hadn’t given any details yet. It’s hard when you don’t know,” she said. “This is Colorado. We have school shootings.”

Pedatto counted herself lucky: she was able to collect her first-grader, Dax, 7, about three hours after the shooting. Other parents waited in the hot recreation center for the buses to deliver their kids, pacing the indoor walking track or sitting on the basketball court near a whiteboard reading “Kids currently ready for reunification” and 11 names.

Many parents still in work uniforms held tight to their sobbing children, offering the reassurance of home-cooked dinners and the chance to get back belongings left behind in the evacuation.

"The heart of all Colorado is with the victims and their families,” Colorado Gov. Jared Polis said in a statement.

Tactical teams searched the area Tuesday afternoon as the STEM school was on lockdown and all other Douglas County schools were on lockout, the school district said. Lines of firetrucks, ambulances and law enforcement vehicles rushed to the scene along with medical helicopters.

Robert Helfer, 13, hugs his grandfather, Shawn Helfer, 57, following a school shooting near Denver on Tuesday.(Photo: Trevor Hughes, AP)

No police officer is assigned to the school, Spurlock said, adding the school has private security. Authorities are waiting for a search warrant to inspect a suspect's car at the school and their homes. Deputies recovered at least one handgun from the suspects, Spurlock confirmed.

“Our prayers are with the victims, family members, and all those affected by today’s shooting at STEM School Highlands Ranch in Littleton, Colorado," the White House said in a statement. "Tragically, this community and those surrounding it know all too well these hateful and horrible acts of violence."

Residents in the area described frightened parents arriving amid confusion and worry.

“I heard a lot of loud bangs but then my boss’s dogs started barking. Next thing you know you hear all the cops coming in and all these kids running out,” said nanny Vanessa Valenzuela, 24, who was working across the street. “I kind of got scared when all these parents were just running into the school and you could tell they were all really upset.”

"It is not enough to send thoughts and prayers, it is empty, it is weak, and it does an injustice to our children who are on the frontlines of this violence," Crow said in a statement. “We must pass common-sense gun violence laws and ensure we are preparing our educators and law enforcement with the tools and resources necessary to create a safe and welcoming environment."

The STEM school will be closed for the remainder of the week, Superintendent Thomas S. Tucker said in a letter to parents that was also posted on the district's Twitter account.

"We are a united family," Tucker wrote. "We are here to support each and every one of you – students, parents and staff – and will continue to do so as long as needed. Together, we will get through this difficult time."

Police and school administrators load students onto school buses following a shooting at STEM School Highlands Ranch, a charter middle school in the Denver suburb of Highlands Ranch, Colo. Trevor Hughes, USA TODAY